Plasticizers are incorporated into a resin (usually a plastic or elastomer) to increase the flexibility, workability, or distensibility of the resin. The largest use of plasticizers is in the production of “plasticized” or flexible polyvinyl chloride (PVC) products. Typical uses of plasticized PVC include films, sheets, tubing, coated fabrics, wire and cable insulation and jacketing, toys, flooring materials such as vinyl sheet flooring or vinyl floor tiles, adhesives, sealants, inks, and medical products such as blood bags and tubing, and the like.
Other polymer systems that use small amounts of plasticizers include polyvinyl butyral, acrylic polymers, nylon, polyolefins, polyurethanes, and certain fluoroplastics. Plasticizers can also be used with rubber (although often these materials fall under the definition of extenders for rubber rather than plasticizers). A listing of the major plasticizers and their compatibilities with different polymer systems is provided in “Plasticizers,” A. D. Godwin, in Applied Polymer Science 21st Century, edited by C. D. Craver and C. E. Carraher, Elsevier (2000); pp. 157-175.
Plasticizers can be characterized on the basis of their chemical structure. The most important chemical class of plasticizers is phthalic acid esters, which accounted for about 85% worldwide of PVC plasticizer usage in 2002. However, in the recent past there has been an effort to decrease the use of phthalate esters as plasticizers in PVC, particularly in end uses where the product contacts food, such as bottle cap liners and sealants, medical and food films, or for medical examination gloves, blood bags, and IV delivery systems, flexible tubing, or for toys, and the like. For these and most other uses of plasticized polymer systems, however, a successful substitute for phthalate esters has heretofore not materialized.
One such suggested substitute for phthalates are esters based on cyclohexanoic acid. In the late 1990's and early 2000's, various compositions based on cyclohexanoate, cyclohexanedioates, and cyclohexanepolyoate esters were said to be useful for a range of goods from semi-rigid to highly flexible materials. See, for instance, WO 99/32427, WO 2004/046078, WO 2003/029339, WO 2004/046078, U.S. Application No. 2006-0247461, and U.S. Pat. No. 7,297,738.
Other suggested substitutes include esters based on benzoic acid (see, for instance, U.S. Pat. No. 6,740,254, and also PCT Publication No. WO2009/118261A1, and polyketones, such as described in 6,777,514; and also co-pending, commonly-assigned, U.S. Patent Publication No. 2008-0242895. Epoxidized soybean oil, which has much longer alkyl groups (C16 to C18) has been tried as a plasticizer, but is generally used as a PVC stabilizer. Stabilizers are used in much lower concentrations than plasticizers. Copending and commonly assigned U.S. Patent Publication No. US 2010-0159177 discloses triglycerides with a total carbon number of the triester groups between 20 and 25, produced by esterification of glycerol with a combination of acids derived from the hydroformylation and subsequent oxidation of C3 to C9 olefins, having excellent compatibility with a wide variety of resins and that can be made with a high throughput.
U.S. Pat. No. 2,476,252 discloses di-ester reaction products of styrene epoxide with carboxylic acids having 3 to 11 carbon atoms which find use as plasticizers for natural or synthetic resins.
U.S. Pat. No. 2,817,673 discloses esters of dicyclopentadiene, wherein dicyclopentadiene is hydroformylated in the presence of water gas (H2/CO) to form dicyclodecane-dimethylal, which is further converted to dicyclodecane-dimethylol, then to the corresponding dicarboxylic acid, and subsequently esterified with lower alcohols. The esters so-formed are disclosed to be useful as softeners and as high grade lubricating oils.
U.S. Pat. No. 4,390,717 discloses a process for preparing mono- or di-carboxylic acid esters of dicyclopentadiene by reacting the dicyclopentadiene with carbon monoxide and an alcohol in the presence of a cobalt catalyst. The cycloaliphatic carboxylates so-formed can be used as a plasticizer or lubricant.
U.S. Pat. No. 4,528,396 discloses dicyclopentadiene-derived ester compounds useful as plasticizers, lubricants, solvents and fuel additives.
Japanese Patent Application Publication Number P 2001-207002 describes 1,2-dicarboxylic acid esters of cyclohexane derived from mixtures containing from 80 to 97 wt % of C9 branched alcohols. JP 2001-207002 compares, as plasticizers, these esters with dioctyl phthalate and finds improved cold resistance, viscosity and viscosity stability over time.
U.S. Pat. No. 7,297,738, incorporated herein by reference in its entirety, discloses esters of cyclohexane polycarboxylic acids which are used as plasticizers for polyvinyl chloride. However, only 1,2-diesters of cyclohexane are disclosed.
Thus what is needed is a method of making a general purpose non-phthalate plasticizer having and providing a plasticizer having suitable melting or chemical and thermal stability, pour point, glass transition, increased compatibility, good performance and low temperature properties.